Numerous attempts have been made at achieving waterproof, breathable footwear. Early attempts for making such footwear included the making of footwear having upper materials (i.e. leather) that were treated to make the upper water resistant as well as soles made of rubber. Several problems, however, arose with this type of footwear construction. The upper material would lose its breathability when it was treated to impart water resistance, thus making the footwear uncomfortable for the wearer. Further, the connecting region between the waterproof sole and the upper became a major source of leakage as there was no known effective way to make the connecting region waterproof.
An alternative approach to the goal of achieving comfortable waterproof footwear involved employing a waterproof insert or bootie into the shoe. This waterproof insert, if constructed of appropriate materials had the additional advantage of being permeable to water vapor so that there was limited buildup of water vapor within the shoe over the time when the shoe was being worn. In the footwear art materials which are both waterproof and water vapor permeable are commonly referred to as “functional” materials. Exemplary of such a functional material is a microporous, expanded polytetrafluoroethylene membrane material available from W. L. Gore and Associates, Inc., Elkton, Md., under the trade name GORE-TEX® Other functional materials have also been developed and are well known in the art.
Further approaches have included securing, by a lasting process, a waterproof, breathable liner material to the inside of the footwear upper and sealing the liner material to a waterproof gasket or insole. There have been many different attempts at providing a durable, waterproof seal or connection at the region where the liner material is joined with the waterproof gasket or insole. These attempts have resulted in varying degrees of success.
One problem which often results when forming such waterproof, breathable footwear is that the insertion of the liner or bootie will often result in a poor fitting shoe (i.e., a smaller fit due to the liner being inserted into the already sized shoe upper) and/or poor attachment between the liner or bootie and the shoe upper material, which results in, among other things, a less than desirable appearance of the inside of the footwear (i.e., the liner appears wrinkled or pulls away from the upper).
A further problem which may result is that during use in wet conditions, water may become trapped between the outer layer of the bootie and the upper resulting in a perceivable weight increase of the footwear. This could result in discomfort for the wearer, especially in cold weather when the wet footwear could result in conductive heat loss.
Thus, there remains a need for footwear that is both lightweight and maintains a high degree of durability and breathability.